The present disclosure relates to a system and method for automated video-based traffic enforcement. The system operates on motion vector data describing the apparent motion in the captured scene. The present disclosure finds application in stop signal enforcement. However, it is appreciated that the present exemplary embodiments are also amendable to other like applications.
Stop signals are generally introduced in regions where conflicting traffic movements can cause a risk of accident. Stop signals often include stop signs, stoplights, and other universal indicators. However, compliance becomes voluntary without use of a physical enforcer, such as an officer or gate. Therefore, multiple methods are introduced to ensure compliance with a signal.
In one conventional method, stoplights are equipped with cameras that capture vehicles entering an intersection. One technology uses an induction loop in communication with the camera, as shown in FIG. 1. The induction loop relies on a vehicle detector module embedded under a road surface near or around a stop (“limit”) line. FIG. 1 shows a first loop that triggers vehicle presence and a second loop that detects a violation. Both loops are activated in quick succession when the stoplight turns red, at which time the controller in communication with the detector automatically sends a signal to the camera, which captures an image of the scene. The vehicle, crossing the intersection, and the red light are both shown in the resulting image. This image is generally provided to a traffic enforcer as visual documentation of a violation. Further sophisticated systems also compute whether the vehicle came to a complete stop by processing a sequence of image frames.
Conventional cameras used to monitor traffic flow and signal compliance can support a variety of surveillance tasks. These cameras are adapted to monitor the scene by continuously capturing video or by controlling the timing to correspond with traffic light changes. These cameras are adapted to transmit the image data to a remote controller using video compression.
However, the process of relaying the image data to the controller is inefficient. The underlying communication network has bandwidth constraints that dictate the use of video compression techniques at the camera end and prior to transmission. Video compression is achieved by exploiting spatial redundancies within a video frame and temporal redundancies across video frames. Spatial redundancies refer to the fact that spatially adjacent pixels are close in value, so compression can be achieved by encoding only variations and/or differences in values between adjacent pixels within a frame. Temporal redundancies refer to the fact that temporally adjacent frames are very similar, so compression can be achieved by encoding only the differences between adjacent frames because the frames capture the same instant over a short time.
The compressed data, for an entire video sequence, is relayed to the central controller where the entire image data is decompressed and analyzed. This process of executing the video analytics tasks on the uncompressed video can result in an increased data processing burden. A reduction in computation time and resources is therefore desired.
The present disclosure provides a more efficient use of video data by determining a violator in a region being monitored as the captured image data is being compressed. Alternatively, the present disclosure can be executed on already compressed video streams without requiring that the entire data be fully decompressed. Other embodiments contemplate determining a violator on a region being monitored by processing motion vectors obtained from other processes such as optical flow and feature correspondence computation.